xen: update Kconfig to allow 64-bit Xen

Allow Xen to be enabled on 64-bit.

Also extend domain size limit from 8 GB (on 32-bit) to 32 GB on 64-bit.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/xen/Kconfig

@@ -6,8 +6,8 @@ config XEN
 	bool "Xen guest support"
 	select PARAVIRT
 	select PARAVIRT_CLOCK
-	depends on X86_32
-	depends on X86_CMPXCHG && X86_TSC && X86_PAE && !(X86_VISWS || X86_VOYAGER)
+	depends on X86_64 || (X86_32 && X86_PAE && !(X86_VISWS || X86_VOYAGER))
+	depends on X86_CMPXCHG && X86_TSC
 	help
 	  This is the Linux Xen port.  Enabling this will allow the
 	  kernel to boot in a paravirtualized environment under the
@@ -15,7 +15,8 @@ config XEN
 
 config XEN_MAX_DOMAIN_MEMORY
        int "Maximum allowed size of a domain in gigabytes"
-       default 8
+       default 8 if X86_32
+       default 32 if X86_64
        depends on XEN
        help
          The pseudo-physical to machine address array is sized